[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] [PATCH] xen: update machine_to_phys_order on resume
>>> On 15.07.11 at 20:23, Keir Fraser <keir.xen@xxxxxxxxx> wrote: > On 15/07/2011 18:30, "Jan Beulich" <JBeulich@xxxxxxxxxx> wrote: > >> Actually, one more thought: What's the purpose of this hypercall if >> it is set in stone what values it ought to return? Isn't a guest using >> it (supposed to be) advertising that it can deal with the values being >> variable (and it was just overlooked so far that this doesn't only >> include varying values from boot to boot, but also migration)? Or in >> other words, if we found a need to relocate the M2P table or grow >> its static maximum size, it would be impossible to migrate guests >> from an old to a new hypervisor. > > Fair point. There has to be a static fallback set of return values for old > guests. Hmm, in my reading the two sentences sort of contradict each other. That is, I'm not certain what route we want to go here: Keep things the way they are after 23706:3dd399873c9e, and introduce a completely new discovery mechanism if we find it necessary to change the M2P table's location and/or size, including a mechanism for a guest to announce it's capable of dealing with that? If so, I think we ought to add a comment to the hypercall implementation documenting that its return values must not be changed (and why). Jan _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxxxxxxxx http://lists.xensource.com/xen-devel
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